1. Field of the Invention
The present invention relates to a remote control circuit for a video cassette tape recorder, and more particularly to a remote control circuit for a video cassette tape recorder (VCR), which is capable of controlling a single VCR, to which several television receivers are connected in common, by utilizing a remote controller at either TV-side.
2. Description of the Prior Art
Referring to FIG. 1, which shows a general remote control circuit for a VCR, the remote control circuit comprises a remote control transmitter 10 for transmitting various key signals selected by the user, in the form of infrared ray signals, a remote control receiver 20 for receiving the infrared ray signal transmitted from the remote control transmitter 10 and decoding the infrared ray signal by a photoelectric conversion thereof, to generate a corresponding system drive signal, and a microprocessor 30 for receiving a system drive signal from the remote control receiver 20 and analyzing composed code information corresponding to the received system drive signal, to output a corresponding system drive control signal.
The remote control transmitter 10 includes a key matrix 11 adapted to generate various key signals selected by the user, a transmission-control microprocessor 12 adapted to scan a key signal from the key matrix 11 and output code information corresponding to the scanned key signal and an infrared ray transmitting unit 13 adapted to transmit the code information from the transmission-control microprocessor 12 to the remote control receiver 20, in the form of a near infrared ray signal. On the other hand, the remote control receiver 20 includes an infrared ray receiving unit 21 adapted to receive the infrared ray signal from the remote control transmitter 10 and convert it into an electric signal, an amplifying unit 22 adapted to amplify an output signal from the infrared ray receiving unit 21 to a predetermined level, a filtering unit 23 adapted to filter an output signal from the amplifying unit 22, a detecting unit 24 adapted to detect code information from an output signal from the filtering unit 24, and a wave-shaping unit 25 adapted to wave-shape an output signal from the detecting unit 24 and apply it to the microprocessor 30.
The operation of the conventional remote control circuit with the above-mentioned arrangement will now be described, in conjunction with FIGS. 2A to 2E.
When the user pushes a desired key on the key matrix 11, the transmission-control microprocessor 12 scans a key signal outputted from the key matrix 11 in response to the pushing of key and outputs code information corresponding to the key signal, as shown in FIG. 2A. By the code information signal from the transmission control microprocessor 12, a transistor Q1 of the infrared ray transmitting unit 13 is switched to turn on/off a light emitting diode PD1, thereby causing the infrared ray transmitting unit 13 to transmit a near infrared ray signal.
As the near infrared ray signal is transmitted from the remote control transmitter 10, by the above-mentioned procedure, it is received in a phototransistor PT1 of the infrared ray receiving unit 20, so that the phototransistor PT1 is turned on/off, to convert the received infrared ray signal into an electric signal shown in FIG. 2B. At this time, the signal outputted from the phototransistor PT1 has very weak intensity, as shown in FIG. 2B, and is thus amplified to an appropriate level, so that a signal as shown in FIG. 2C is outputted therefrom.
Thereafter, the output signal from the amplifying unit 22 is filtered in the filtering unit 23 and then is detected in the detecting unit 24 as a signal as shown in FIG. 2D. The detected signal is then wave-shaped into a signal having a waveform shown in FIG. 2E, in the wave-shaping unit 25, and then applied to the microprocessor 30 for controlling the overall system. The microprocessor 30 analyzes codes composed into the waveform shown in FIG. 2E and outputs a system control signal (CTL) indicative of the analyzed result. Accordingly, the operation of system can be controlled by key inputs from the remote control transmitter 10.
In case of such a conventional remote control system, however, one remote control transmitter can control only one appliance corresponding thereto. Where a TV system is connected to a VCR at a remote location from the VCR, or several TV systems disposed at different rooms are connected to one VCR, the VCR can not be controlled at the TV-side. As a result, in case of operating the VCR, the user should go to the position of VCR and then manipulate a remote control transmitter or control keys on VCR, thereby resulting in the troublesome operation.